Fermentor performance

Shu (S6) has taken advantage of the dependence of fermentor performance on agitator speed, by setting up a feedback control loop in which the agitator speed is varied automatically so as to cause the broth oxygen uptake to vary with time in a predetermined manner. 

Data in Table 7.1 show how the substrate concentration in the feed can affect fermentor performance. 

Bakers Yeast Production. Bakers yeast is grown aerobicaHy in fed-batch fermentors under conditions of carbohydrate limitation. This maximizes the yield of yeast biomass and minimizes the production of ethanol. Yeasts grown under these conditions have exceUent dough leavening capabHity and perform much better in the bakery than yeast grown under anaerobic conditions. 

We will now deal with quite sophisticated issues concerning reactor design and performance. Although we deal with these in a sympathetic manner, you may find it useful to refresh your knowledge by reading more about bioreactors. The BIOTOL series offers opportunities to learn more about fermentors. 

Due to the potential for endo-pectinase production shown by the hybrid H15 on lemon peel, studies on fermentor using 3% lemon peel were performed. As shown in Figure 2A, maximum endopectinolytic activity was 80.0 U ml which is higher (60%) than the activity produced by hybrid H15 in 500 ml Erlenmeyer flasks we had previously observed in... 

Some very nice engineering and experimental work was performed by Pollard et al. in measuring a fungal fermentation in real time.21 The work was performed on a 75-1 fermentor and showed detection limits for fructose, glutamate, and proline in production matrices of 0.1,0.5, and 0.5 g/1, respectively. Glucose and phosphate were measured in a 280-1 pilot scale batch with detection limits for both of 0.1 g/1. 

With both feed and cells entering the fermentor, the Monod expression (Eq. 1) in the performance expression for the MFR (Eq. 6) gives... 

Bioreactors are the apparatus in which practical biochemical reactions are performed, often with the use of enzymes and/or living cells. Bioreactors that use living cells are usually called fermentors, and specific aspects of these are discussed in Chapter 12. Ihe apparatus applied to waste water treatment using biochemical reactions is another example of a bioreactor. Even blood oxygenators, that is, artificial lungs as discussed in Chapter 15, can also be regarded as bioreactors. 

In order to evaluate the performance of the fermentor as an ethanol producer, we calculate the conversion of substrate, the product yield of ethanol and its productivity according to the following simple relations ... 

Because ethanol fermentation is inhibited by product, the selective extraction of ethanol during fermentation is also important to improve process performance. Silva et al. (3) have reported that the scheme that combines a fermentor with a vacuum flash vessel presents many positive features and good performance when compared to a conventional process (4). 

The present state of development in biosensors is at a level where the sensor is used outside the bioreactor. This step has been taken because of sterility problems with the bioreactor and stability problems concerning the biosensor. As long as no sterilizable biosensor is available, most of the applications must be performed outside the fermentor. In such cases, leakage will cause no practical problems, except that more enzyme may be needed. 

Nienow, A.W. Gas dispersion performance in fermentor operation. Chem. Eng. Progr. 1990, 61-71. 

The operating conditions for solid-state fermentation for cellulase production are dependent on the strain to be used, the reactor type and the medium composition, but the basic operating procedure remains the same as shown in Fig. 2. The final product can be obtained as crude solid cellulase, liquid cellulase or powder cellulase according to the application. Figure 3 shows a process flowsheet for cellulase production [25]. In the process, wheat bran is used as substrate. Seeds are prepared in a stirred-tank fermentor and then sprayed into the medium by a spray distributor. The fermentation is performed in a shallow-tray fermentor. The temperature and humidity in the fermentor are automatically regulated. After fermentation, cellulase is recovered by water extraction and purified by salt precipitation and ion exchange. The final product is concentrat-... 

Yang et al. [26] used xylose as the carbon source for Rhizopus to grow into mycelial pellets (about 1 mm in diameter). With these restricted mycelial pellets, lactic acid was produced readily and the pellets could be used repeatedly over a 22-d period with good acid yield. When PVP was incorporated into the fermentation system, lactic acid was also produced in the absence of the neutralizing agent. With this fermentor/adsorber system, fermentation can be performed as effectively as when CaCOj is used (see Fig. 2 for schematic diagram of the fermentation system). 

Table 7.1 Comparison of Performances of Different Fermentor Configurations for Lactose to Ethanol Conversion by Kluyveromyces fragilis...

Table 7.2 Comparison of Performances of Different Fermentors for Glucose to Lactic Acid Transformation by Lactobacillus delbreuckii...

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